In general, the following forms of leaching copper from a copper sulfide ore by a hydrometallurgical process are known: a form of leaching by a batch-wise stirring reaction using sulfuric acid or hydrochloric acid; a form of leaching by preparing a heap of the ore, providing sulfuric acid or hydrochloric acid to the top of the heap and recovering the liquid dropped by gravity (heap-leaching method); and the like. Also known is a method by utilizing the ability of bacteria such as iron oxidizing microbes for leaching and recovering the copper efficiently (bioleaching).
As for the hydrometallurgical process of the copper sulfide ore, a bioleaching method and the like have been put to practical use for a secondary copper sulfide ore such as chalcocite, covelline and the like. On the other hand, there is a problem that as the solubility of a primary copper sulfide ore such as chalcopyrite to mineral acids is very low, the leaching rate thereof is very low when the leaching is performed at ordinary room temperature.
With regard to the above-described problem, Japanese Patent Application No. 2009-193197 (Patent Document 1) which has not yet been laid open, reports the example that the leaching of a copper sulfide ore mainly including chalcopyrite and enargite is promoted at ordinary room temperature in the presence of an iodide ion together with an iron (III) ion as an oxidizing reagent. In the leaching, it is also desirable economically to prepare and provide the iron (III) ion used as an oxidizing reagent by oxidizing with the iron oxidizing microbes an iron (II) ion obtained as the result of the leaching reaction or inexpensive ferrous sulfate.
It is also desirable economically and environmentally that the post-leaching solution is reused as a leaching solution repeatedly without being discarded. However, it had been difficult to reproduce the iron (III) ion by using the iron oxidizing microbes in said leaching wherein a solution containing iodide ion is used. This is because there had been a problem that the iodide ion is converted into a molecular iodine, triiodide ion and the like, which prevent the iron oxidizing microbes from oxidizing iron and inhibit the proliferation of said microbes,
In Japanese Patent Application No. 2010-060037, which has not yet been laid open, the applicant of the present application then proposed a method, wherein the iron (II) ion in the solution is oxidized into the iron (III) ion by the iron oxidizing microbes, after decreasing an amount of the iodine(s) in the post-leaching solution by using activated carbon.
Furthermore, in Japanese Patent Application No. 2010-128300 (Patent document 3), which has not yet been laid open, the applicant of the present application reported a method wherein the activated carbon and the iron oxidizing bacteria are used in the same reaction system, and thus, the oxidation of the iron (II) ion and the adsorption of the iodine(s) by the activated carbon are performed simultaneously.
Apart from the above-described field, Japanese Patent Application Publication No. S47-38981 (Patent document 4) reports an example of a reactor for continuously oxidizing iron in which iron oxide sludge is used as an immobilizing carrier for the iron oxidizing microbes. However, in said document, the invention is applied to treating acidic mine water containing an iron (II) ion in a sulfur mine and the like, but not studied for applying it to treating the leaching solution containing the iodide ion.